Welded inlet pipe and nozzle box construction for steam turbines

ABSTRACT

A welded inlet pipe and nozzle box construction for a steam turbine which provides flexible support for the nozzle box. The flexing portions of the construction subject to high stress are in a weld-free location, while the main weld connecting the nozzle box to the turbine shell is located to prevent leakage into the power station should a defect occur.

0 United States Patent 1151 3,659,956 Brinkman 14 1 May 2, 1972 54] WELDED INLET PIPE AND NOZZLE 2,527,445 10/1950 Pentheny.....i ..41s/13s 2,527,446 10/1950 Jenk, Jr. eta. ...415/139 ggg ggg FOR STEAM 2,651,495 9/1953 Corbett ...4l5/l39 2,823,891 2/1958 Baker et al.. ...4l5/108 2 Inventor; Ear] Bfl k Schenectady N 2,925,995 2/1960 Hertl ..4l5/l38 [73] Assignee: General Electric Company P i E mi er-Henry F, Raduazo Attorney-William C. Cruteher, James W. Mitchell, Frank L. [221 1970 Neuhauser, Oscar B. Waddell and Joseph B. Forman 211 Appl. No.: 97,560

[57] ABSTRACT [52] U.S. Cl ..415/219, 415/108, 415/138, A welded inlet pipe and nozzle box construction for a steam 415/100 turbine which provides flexible support for the nozzle box. [51 Int. Cl ..F01d l/00, F04d l/08 The flexing portions of the construction subject to high stress [58] Field at Search ..4l5/108, 138, 139, 199, 219, re in a -fr lo i n. whil he m in eld connecting 415/100 the nozzle box to the turbine shell is located to prevent leakage into the power station should a defect occur. [5 6] Meme Cited 4 Claims, 3 Drawing Figures UNITED STATES PATENTS 2,112,738 5/1938 Doran ..4l5/108 pie 13 Patented May 2, 1972 3,659,956

2 Sheets-Sheet 1 F|G.| I v f 2 I l 8 i L I I 4 I INVENTOR:

EARL H. BRINKMAN,

BY M

HIS ATTORNEY Patehted May 2, 1972 2 Sheets-Sheet 2 INVENTORZ EARL H. BRINKMAN,

BY 40.6" M

HIS ATTORNEY.

WELDED INLET PIPE AND NOZZLE BOX CONSTRUCTION FOR STEAM TURBINES BACKGROUND OF THE INVENTION This invention relates generally to a construction for attaching stationary nozzle boxes inside a steam turbine shell so as to allow relative thermal movements between the parts when hot steam is supplied through an inlet pipe to the nozzle box. More particularly, the invention relates to a welded inlet pipe and nozzle box construction suitable for using steam generated by a nuclear reactor.

The problems of conducting steam from a steam generator or steam reheater into a stationary turbine shell and supplying it to the rotating blades by means of arcuate nozzle boxes are well known in the steam turbine art. Known constructions include provisions for thermal expansion and contraction of the steam inlet pipe with respect to the turbine shell by means of collars, expansion loops, or multiple ring sliding joints. The problem always involves the bringing of a pipe or conduit through an opening in the steam turbine shell (or through two openings if it happens to be a double casing construction) to a nozzle box located inside the shell. Means must be provided to seal the opening around the conduit, to provide for thermal expansion and contraction of the nozzle box with respect to the shell, and to support the nozzle box within the shell.

Although many constructions have been shown in the art for carrying out the aforementioned functions so that the parts can later be disassembled, the advent of nuclear reactors for providing energy to supply the steam has led to the desirability of integral or welded connections to prevent the possible leakage of steam into the power station. The prior art has suggested welded constructions, but those known place the welds in highly stressed or inaccessible locations where incipient crack formation cannot be easily detected.

Accordingly, one object of the present invention is to provide an improved welded inlet pipe and nozzle box construction for a steam turbine.

Another object of the invention is to provide an improved welded joint configuration for supporting a steam turbine nozzle box which permits thermal movements thereof with respect to the shell without overstressing the weld.

DRAWING The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of practice, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which:

FIG. 1 is a vertical elevation drawing, in section, of the upper portion of an opposed flow steam turbine,

FIG. 2 is a view looking in an axial direction of the upper half of the shell of the turbine of FIG. 1, taken along lines II II, and

FIG. 3 is an enlarged cross section view of one of the welded joints shown in FIGS. 1 and 2.

SUMMARY OF THE INVENTION Briefly stated, the invention is practiced by providing a special flanged portion comprising the turbine shell opening. The flanged portion forms part of the expansion loop and also comprises a section of the steam inlet pipe itself. The nozzle box pipe is attached to the radially inner edge of the flanged portion by an inside weld, while the steam supply pipe is connected to the radially outer edge of the flanged portion by an outside weld.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawing, the invention is shown as applied to an opposed flow single shell steam turbine, although the principles of construction are equally applicable to single flow steam turbines and also can be applied to the inner shells of double-shell steam turbines if desired.

In FIG. 1, the turbine shell shown at l is supplied with steam from four inlet pipes, one of which is indicated by reference numeral 2. A rotor 3 having stages of turbine buckets 4 thereon, is disposed for rotation within shell 1. Also several stages of stationary diaphragms 5 are supported by the shell and serve to direct steam flow through the turbine buckets 4.

Also supported within the shell and connected to receive steam from each of inlet pipes 2 is a nozzle box 6, which here is of the double ended or back-to-back type, although it could equally well be of the single flow type directing steam in only one axial direction.

In accordance with the invention, the opening through shell 1 comprises an integral flanged portion 7 which is offset outward from the shell proper by an integral expansion loop 8.

Further details of the invention will become apparent by reference to FIG. 2 which is a view looking in the axial direction. There it is seen that the upper half of the shell 1 is supplied with two inlet pipes 2 having oppositely directed flanged connections 9 for connection to the steam supply piping. The lower half of shell 1 is similarly constructed and also has two inlet pipes and therefore is not shown.

Each of the nozzle boxes 6 is constructed to admit steam around a arc and in the present embodiment, in opposed axial directions as well. The details of the nozzle box 6 are not material to the present invention except to note that the nozzle box is supported by and also supplied by a nozzle pipe section 10. Other means to provide restraint of the nozzle box, such as lugs 11, may be provided to prevent movement in axial or other directions while allowing for thermal movements.

The opening through turbine shell 1 consists of a outwardly offset flanged portion having an outer circumferential edge 12 and an inner circumferential edge 13. The flanged portion 7 is an integral part of shell I and is formed therein to include a gently curved wall portion 8 of integral shell parent metal branching from the middle of flange 7, which is arranged to serve as a flexture location or an expansion loop. The portion 7 between edges 12, 13 serves as an intermediate section of the steam inlet conduit to nozzle box 6.

Still further details may be seen by reference to the enlarged view in FIG. 3. The joint shown is typical and it will be understood by those skilled in the art that the wall thicknesses herein shown for a large steam turbine may be on the order of 3 in. thick and the inside diameter of the opening shown on the order of 2 ft. The flanged portion 7 is formed from the integral rough cast shell by machining. The expansion loop 8 is formed by an outwardly curving wall portion 14 formed on a suitable radius, i.e., on the order of 5 in., then thinning somewhat and curving inwardly toward the opening by means of wall portion 15. The inside cylindrical surface of flanged portion 7 is machined for the passage of steam and the inner and outer edges l2, 13 are prepared for receipt of weld metal.

After the end of nozzle pipe 10 is brought into position with the inner edge 13, a 3 oclock" weld 16 is made from the inside of the pipe (hereinafter termed an inside weld"), preferably by means of automatic submerged arc weld equipment.

Subsequently, after the inside weld 16 is cleaned and found to be satisfactory, the inlet pipe 2 is brought into alignment with the outer edge 12 of flanged portion 7 and a weld from outside the pipe or outside weld" 17 is made to complete the assembly. The finished welds or weldments l6, 17 are wider on the side from which made, as known to those skilled in one art. Thus the heat-affected zone of weld 16 does not extend into the expansion loop 8, since the weld is commenced at the juncture 16a some distance from loop 8.

OPERATION In operation, expansion and contraction of the nozzle pipe 10 is taken with respect to turbine shell 1 by means of flexture in the expansion loop 8. The most highly stressed portion of In [nil mu the expansion loop comprises parent shell metal, free from the heat-affected zone of the welds 16 and 17.

The inside weld 16 is located in a straight section of nozzle box piping away from the more highly stressed parts of the expansion joint 8. Should a defect occur in the inside weld 16, it will be observed that steam leaks will occur into the inside of the shell 1 rather than into the power station as would be the case with many prior art constructions.

Steam in its passage to the nozzle box from the inlet pipe 2 flows through flanged portion 7, which is a portion of the shell itself, before it flows into the nozzle pipe 10. Thus any thermal stresses which might develop at this critical juncture are again located in the shell metal, rather than in a weld heat-affected zone.

While there has been shown what is considered to be the preferred embodiment of the invention, it is of course understood that various other modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a steam turbine having a shell containing a noule box spaced inside the shell, the improvement comprising:

a shell flanged portion integral with said shell having inner and outer annular edges and defining an opening through the shell,

a nozzle pipe projecting from and adapted to supply steam to said nozzle box and means connecting said flanged portion inner edge to said nozzle pipe by an inside weld, and

a steam inlet pipe having an end connected to said outer edge of the flanged portion by an outside weld, whereby said inlet pipe, said flanged portion and said nozzle pipe together fonn a steam inlet passage to the nozzle box.

2. The combination according to claim 1, wherein said flanged portion is outwardly offset from the wall of said turbine shell by a connecting curved wall section arranged to serve as an expansion loop for said steam inlet passage with respect to the shell.

3, The combination according to claim 1, wherein said flanged portion is connected near the middle thereof to the turbine shell by an integral shell wall portion having a curving cross section adapted to flex near the juncture of said shell wall portion and said flanged portion.

4. In a steam turbine having a shell containing at least one arcuate nozzle box spaced inside the shell, conduit means for conducting steam to said nozzle box from a source of steam, said conduit means comprising:

an inlet pipe section disposed outside said shell and communicating with said steam source,

a nozzle pipe section disposed inside said shell and connected to supply and to support said noule box, and

an intermediate section connected between said nozzle pipe and said inlet pipe by inside and outside welds respectively, said intermediate section being an integral portion of the shell and defining an opening through the shell, said intermediate section having near the middle thereof an integral expansion loop permitting relative movements between the shell and said conduit means.

i i 1 i i 

1. In a steam turbine having a shell containing a nozzle box spaced inside the shell, the improvement comprising: a shell flanged portion integral with said shell having inner and outer annular edges and defining an opening through the shell, a nozzle pipe projecting from and adapted to supply steam to said nozzle box and means connecting said flanged portion inner edge to said nozzle pipe by an inside weld, and a steam inlet pipe having an end connected to said outer edge of the flanged portion by an outside weld, whereby said inlet pipe, said flanged portion and said nozzle pipe together form a steam inlet passage to the nozzle box.
 2. The combination according to claim 1, wherein said flanged portion is outwardly offset from the wall of said turbine shell by a connecting curved wall section arranged to serve as an expansion loop for said steam inlet passage with respect to the shell.
 3. The combination according to claim 1, wherein said flanged portion is connected near the middle thereof to the turbine shell by an integral shell wall portion having a curving cross section adapted to flex near the juncture of said shell wall portion and said flanged portion.
 4. In a steam turbine having a shell containing at least one arcuate nozzle box spaced inside the shell, conduit means for conducting steam to said nozzle box from a source of steam, said conduit means comprising: an inlet pipe section disposed outside said shell and communicating with said steam source, a nozzle pipe section disposed inside said shell and connected to supply and to support said nozzle box, and an intermediate section connected between said nozzle pipe and said inlet pipe by inside and outside welds respectively, said intermediate section being an integral portion of the Shell and defining an opening through the shell, said intermediate section having near the middle thereof an integral expansion loop permitting relative movements between the shell and said conduit means. 